In recent years, it has become trendier in the industrial field to manufacture various products, each in smaller and smaller quantities. To manufacture various products with a single press apparatus, it is necessary to replace a die for making a product, with another die for manufacturing another product. Recently, a die quick-changing (DQC) system has been developed to shorten the time required for replacing dies. Generally the DQC system comprises two movable bolsters. While one bolster is operating, the die to be used next is set on the other bolster. That is, a die is replaced with another as the first bolster is replaced with the second bolster. A die is set up every time before it is used to replace another die.
A press apparatus may perform press working at several parts of a work. If the parts of the work differ in position, different dies must be used even if all parts of the work have the same shape. In such a case, a die is replaced with another to conduct press working on a new part of the work.
There is known another method of performing press working on several parts of a work. In this method, a plurality of press apparatuses are arranged side by side, and the work is moved to these press apparatuses sequentially, undergoing press working at each press apparatus. In this method, the press apparatuses, each having a different die, are used in the same number as the parts of the work which assume different positions and which must be press-worked.
With the press apparatuses hitherto used in general, such as crank press and toggle press, it is necessary to adjust the bottom dead center of the slider in accordance with the die employed. Every time a die replaces another, its position needs to be adjusted not only in the X and Y directions, but also in the Z direction. Hence, it would take a long time to set up the die to replace another die even in the conventional DQC system. It is therefore difficult to achieve a substantial improvement.
A plurality of press apparatuses used to perform press working on several parts of a work can serve to manufacture but one type of a product, unless the die attached to each apparatus is replaced by another. This is because each press apparatus cannot have its position adjusted.